Preparation of fluorocarbon phosphines



United States Patent Q PREPARATION OF FLUOROCARBON PHOSPHIN ES Anton B.Burg and Walter Mahler, Los Angeles, Calif., assignors, by mesneassignments, to American Potash & Chemical Corporation, a-corporation ofDelaware No Drawing. Application June 7, 1957 Serial No. 664,183

9 Claims. (Cl. 260606.5)

This invention relates in general to the preparation of fiuoroalkylphosphines and more particularly to a method by means of whichbis(fluoroalkyl) phosphorous halides may be treated with mercury in thepresence of protonic, non-oxidizing acids, to produce alkyl phosphines.

The conventional manner in which fiuoroalkyl phosphines of the type (CFPI-I are'prepared is by the catalytic reduction of fluorocarbonphosphorous iodides by hydrogen. This is the method of Bennett, Emelusand Haszeldine, reported in J. Chem. Soc., 1954-, 3901. The method isfairly satisfactory where only small quantities of the product aredesired, but difliculties'are still presented in that the product is notreadily purified, quantities of HF, HI and PH being present.

It is therefore an object of this invention to provide for thepreparation of fluorocarbon phosphines by a method which does notinvolve catalytic reduction of fluorocarbon phosphorous halides.

A further object of this invention is to provide a method which can bereadily practiced at room temperature and which is capable of yieldingfluorocarbon phosphines in good quantity in a relatively short period oftime.

Broadly, it has been found that fluorocarbon phosphines such as (CF PHmay be formed by the action of a metal such as mercury on a fluorocarbonphosphorous halide of the type such as (CF PX, where X represents ahalogen, in the presence of protonic acids lacking any oxidizing powerof a nature which would interefere with the desired result.

More particularly, it has been found that reactions of the type:

are suitable for the preparation of long or short chain fluorocarbonphosphines. As is apparent from the above equation, the method of thisinvention does not involve the formation and use of H but rather theremoval of a halogen followed by replacement by H More particularly, ithas been found that fluorocarbon phosphorous halides, and especially theiodides, may be reacted with mercury in the presence of protonic,nonoxidizing acid so as to yield fluorocarbon phosphines. A preferredembodiment of the invention involves the use of bis(trifluoromethyl)phosphorous iodide with mercury in the presence of HCl, the reactiontaking place in a closed apparatus with a stoichiometric excess of theacid and an adequate pool of mercury, the ingredients being shaken foran hour or less at room temperature. Where it is desired to obtain afaster reaction, the temperature may be raised to as high as 100 C., oreven somewhat higher if desired. The volatile product obtained willcontain the fluorocarbon phosphine which may be separated from P-Plinked products by distillation methods.

As set out earlier, either long or short chain fluorocarbon phosphinesmay be prepared. A wide variety of metals other than mercury aresuitable, a requirement being that they have a good afiinity forhalogens. Of

course, mercury, being a liquid, is most convenient since the reactionmay be encouraged by shaking together the various reactants. Any of avariety of non-oxidizing acids may be used, those set forth in theexamples which follow giving some idea as to the wide range which aresuitable. It is even possible to use water as theproton source, butbecause of hydrolytic side reactions somewhat more acid materialsarepreferred.

In a preferred embodiment of this invention wherein (CF PI and HCl arereacted with mercury, agood yield of (CF PH and P (CF is obtained.Howeventhis reaction produces a certain amountof (CF3) PCl which mayreadily be removed by pure Water hydrolysis. The pure (CF PH finallyobtained generally appears in the yield of about 35% of the original (CFPI. It is also possible first to treat the (CF PI or other-halide withmercury to form a solid residue. This material is then treated with theacid. For example, where HCl is used to treat the solid residue obtainedfrom the reaction of (CF PI and mercury, the product (CF hPl-l'ina yieldamounting to 5% of the original (CF PIhas been obtained. Thisdemonstrates the presence of the linkage HgP(CF .in the intermediateproduct.

It is also somewhat more convenient simply to prepare the (CF PH byusing H PO or CF COOH as the acid instead of HCl, since, in thisfashion, the formation of (CF PCl is avoided. Yields again are in theneighborhood of 35%.

Examples. illustrating the practice of this invention are set forthbelow but are notto be construed as imposing limitations on the scope ofthe invention other than as are set forth in the appended claims.

Example 1 Samples of (CF PI (0.414 g.) and anhydrous HCl (0.0912 g.)were brought together in a closed flask containing 50 g. of mercury andshaken for one hour at room temperature. The voltatile products weredistilled off and separated by means of a high-vacuum distillationaparatus. One by-product was 0.068 g. of the previously known substanceP (CF which could be identi- I fied by its characteristic vapor tensionsand molecular weight. Another by-product was (CF PCl (0.105 g.), whichwas destroyed by the action of pure water. The yield of pure (CF PH was0.083 g., or 35% of the original (CF P units. It was identified by itscharacteristic vapor tensions and molecular weight.

Example II Example III A 3.85 g. sample of (CF P1 was shaken with 10 g.of CF COOH and g. of mercury in a closed container for 20 minutes atroom temperature. The yield of pure (CF PH (which was identified by itscharacteristic physical properties and nuclear-magnetic-resonancespectrum) amounted to 0.774 g., or 35%.

Example IV 2.5 millimol HCl and 1.4 mmol (CF PI were brought into aflask containing 300 g. mercury and shaken together for 2 hours. Thevolatile products were fractionated in high vacuum and consisted of .3mmol (CF P and a mixture of (CF PH and (CF PCl. This mixture wasresolved by destruction of the (CF,),PC1 by a neutral water hydrolysisand .5 mmol (CFQ PH was obtained pure, representing a yield of 35%.

Example V 6.3 mmol (CFQ PI were brought into a flask containing 100 g.Hg and g. of 85% H PO (tech), shaken for 30 minutes and the productsfractionated to give 2.2 millimols (35% yield) of (CF PH. Other productsof this reaction were fluorocarbon phosphines containing oxygen such as(CF ),P(O)H.

Example VI 12.9 mmol (CF hPI were brought into a flask containing 250 g.Hg and 20 g. CF COOH and shaken for 1 hour. Fractionation delivered 4.3mmol of (CF PH, representing a 33% yield. 7

A variety of the fluorocarbon phosphorous halides used as reactants areknown. A preferred method for their preparation is that set forth in theJournal of the American Chemical Society, 79, 247 (1957), The Synthesisof Fluorocarbon Phosphorous Iodides. The method set out there may beapplied with minor modifications to the preparation of other halides.

As can be seen from the foregoing, it is possible by following theteachings of this invention to produce fluorocarbon phosphines in afashion which enables the production of the desired product in fairlylarge yields. These .products may be treated with diborane in thefashion set forth in the co-pending application, Serial No. 663,623,filed June 5, 1957, relating to Fluorocarbon phosphinoborines. As setout in that application, the products which are obtained by thisdiboranefluorocarbon phosphine reaction are polymeric materials havinghigh thermal and chemical resistance which can be used as hydraulicfluids under high temperature conditions. The products of the instantinvention, therefore, are suitable as intermediates in the preparationof these new polymers.

Obviously many modifications and variations of the invention ashereinbefore set forth may be made without departing from the spirit andscope thereof, and therefore only such limitations should be imposed asare indicated in the appended claims.

We claim:

1. A process for the preparation of fluorocarbon phosphines whichcomprises: treating (RCF PX where R is from the group consisting oflower alkyl and fluorine and X is iodo with mercury in the presence of amemher from the group consisting of water and a protonic, non-oxidizingacid and separating said fluorocarbon phosphine so formed from thereaction mixture.

2. The process of claim 1 wherein the acid is hydrochloric acid.

3. The process of claim 1 wherein the acid is phosphoric acid.

4. The process of claim 1 wherein the acid is CF COOH.

5. The process for the preparation of atrifluoromethyl phosphinecomprising: treating (CF PI with mercury in the presence of a protonic,non-oxidizing acid and separating the fluorocarbon phosphine so formedfrom the reaction mixture by fractional distillation.

6. The process of claim 5 wherein the acid material is hydrochloricacid.

7. The process of claim 5 wherein the acid is phosphoric acid.

8. The process of claim 5 wherein the acid is CF COOH.

9. The process of claim 5 wherein the acid material is water.

References Cited in the file of this patent Kosolapotr':Organophosphorus Compounds, John Wiley & Sons, Inc., New York, 1950,pages 15, 16.

1. A PROCESS FOR THE PREPARATIN OF FLUOROCARBON PHOSPHINES WHICHCOMPRISES: TREATING (RCF2)2PX WHERE R IS FROM THE GROUP CONSISTING OFLOWER ALKYL AND FLUORINE AND X IS IODO WITH MERCURY IN THE PRESENCE OF AMEMBER FROM THE GROUP CONSISTING OF WATER AND A PROTONIC, NON-OXIDIZINGACID AND SEPARATING SAID FLUOROCARBON PHOSPHINE SO FORMED FROM THEREACTION MIXTURE.